Parkinson's disease is a prevalent neurodegenerative disorder characterized by tremors, rigidity, and bradykinesia. These symptoms are thought to arise from the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Recently, mutations of the parkin gene, which encodes a ubiquitin-protein ligase, were found to underlie a familial form of Parkinson's disease known as autosomal recessive juvenile Parkinson's disease (AR-JP). While this advance provides clues to the mechanism responsible for pathology in AR-JP, the cellular targets of the parkin ubiquitin-protein ligase activity and the specific biochemical pathways affected by parkin mutations remain largely unknown. To address these issues, the objectives of this proposal are to create a Drosophila melanogaster model of AR-JP through mutational analysis of a Drosophila parkin ortholog, and to use this fly AR-JP model to investigate the molecular mechanisms of neuronal dysfunction underlying parkin deficiency. Two main hypotheses will be explored in this proposal: (a) parkin sequesters alpha-synuclein protein into Lewy bodies and this function represents a cellular mechanism of alpha-synuclein detoxification; (b) neurodegeneration triggered by parkin mutations results from accumulation of parkin substrate(s). To accomplish the objectives of this proposal, the following specific aims will be pursued: (1) Generate and characterize Drosophila parkin (D-parkin) mutants; (2) Determine whether altered D-parkin expression affects the time course and extent of alpha-synuclein induced neurodegeneration and Lewy body formation; (3) Identify modifiers of a D-parkin mutant phenotype; (4) Isolate D-parkin-binding components and investigate structure-function relationships in D-parkin. Results from this work should clarify the relationship between parkin dysfunction and neurodegeneration, and possibly reveal strategies for treatment of Parkinson's disease.